1. Field of the Invention
The present invention relates to a scroll fluid compressor which partitions the interior of an enclosed container into a high pressure section and a low pressure section serving as an accumulator.
2. Description of the Prior Art
Scroll compressors have generally been known which are provided at the outer periphery with a suction chamber and at the center of a spiral with a discharge port so that fluid is taken-in and compressed at a spiral compression space symmetrical with respect to the discharge port, the compressed fluid flowing in one direction and compression torque less in variation than a reciprocation compressor or a rotary compressor, thereby extremely reducing vibrations or noises.
A usual refrigeration system, as shown in FIG. 17, constitutes a refrigeration cycle of a compressor 111, a condenser 112, an expansion valve 113 and an evaporator 114 sequentially connected, in which in order to restrain storage of intake refrigerant and compression of liquid refrigerant apt to occur in a compression chamber of compressor 111 to thereby improve durability of compressor, an accumulator 110 for gas-liquid separation and storage of refrigerant is provided between the suction side of compressor 111 and the evaporator 114, the accumulator 110 is mounted in the vicinity of the side surface of compressor 111, and heat insulation is applied between the accumulator 110 and the compressor 111, whereby intake gas refrigerant is heated following heating of the accumulator 110 so as to prevent the compression efficiency from lowering.
The accumulator 110, as shown in FIG. 18, is so designed that a baffle plate 103 is disposed at the upper end of a center pipe 104, so that the liquid refrigerant returning from the evaporator 114 is prevented from directly flowing into the upper opening of the center pipe 104 connected to the suction side of compressor 111, thus forming a bypass B through which the refrigerant passes (refer to Japanese Laid-Open Utility Model Publication No. 59-84378).
When such an accumulator 110 for gas-liquid separation and storage of refrigerant is mounted on the scroll refrigerant compressor for lessening vibrations and noises, a problem is created in that the intake liquid refrigerant strikes the inner wall or the like at the scroll refrigerant compressor to cause vibrations by the accumulator itself, thereby exciting the scroll refrigerant compressor, and that the refrigerant collision noise transmits to the body 101 that is small in thickness for weight reduction to thereby deteriorate low vibration and low noise characteristics of the scroll compressor.
Another problem is created in that the compressor and accumulator are separate in construction regardless of construction of the compressor so that the compressor and accessories thereof require a large space for disposing them.
To eliminate the above-mentioned problems, it is proposed that the compressor houses therein an accumulator unit for gas-liquid separation as disclosed in the Japanese Patent Publication No. 43-2518. However, this construction is disadvantageous in that the wall area forming the accumulator unit is large and the intake gas refrigerant passes through an electric motor unit, so that the intake gas refrigerant is heated which significantly lowers compression efficiency. Especially, when a large quantity of liquid refrigerant is returned to the compressor in the scroll compressor, liquid compression is apt to occur in the permanently enclosed space in the compression chamber that does not connect with both the suction chamber and the discharge chamber, and an excessive compression load causes damage in the compression chamber-constructing members or breakdown in the bearings, so that some means for reducing the compression load and preventing the liquid compression must be provided.
FIG. 19 shows another scroll compressor, in which an enclosed container 206 is partitioned therein from a scroll compression unit through a frame 209, a low pressure chamber 206b being formed above the frame 209 and a high pressure chamber 206a below the frame. The low pressure chamber 206b gas-liquid separates the refrigerant, and heat quantity transmitted from the high pressure chamber 206a through the enclosed container 206 is used to completely evaporate the intake refrigerant by being heated to a certain extent, after which the refrigerant is taken into the compression chamber through a suction pipe 210 provided at a fixed scroll member 202, thereby preventing the occurrence of liquid compression. After the compressed gas refrigerant is discharged to the high pressure chamber 206a through an outflow path 211, a lubricating oil is separated from the discharged gas refrigerant, an O-ring 214 provided between the frame 209 and the enclosed container 206 is used to seal between the low pressure chamber 206b and the high pressure chamber 206a, a heat insulating material 213 of Teflon mounted on the upper surface of the fixed scroll member 202 reduces heating to liquid refrigerant 219 at the low pressure chamber 206b, and the gas-liquid separation chamber is integral with the enclosed container, thereby expecting space saving, low noises and low vibrations at a time when the compressor is installed (refer to Japanese Laid-Open Patent Publication No. 57-70984).
A scroll compressor with a structure similar to the above-mentioned is also described in specification of the U.S. Pat. No. 4,522,575.
With the structure shown in FIG. 19, since the low pressure chamber 206b is disposed at the upper portion of the scroll compression unit, the liquid refrigerant 219 directly contacts at the outer periphery thereof with the enclosed container 206 at a high temperature and forming the high pressure chamber 206a, thereby creating the problem in that the outer periphery of liquid refrigerant 219 that is higher in density than gas refrigerant and that is superior in thermal conductivity and the intake gas refrigerant above the liquid refrigerant 219 are heated to lower the compression efficiency.
When the wall constituting the low pressure chamber 206b at the enclosed container 206 is larger in thickness, refrigerant noises caused by the intake gas refrigerant flowing into the low pressure chamber 206b to strike the inner wall thereof and the resonant noises of enclosed container 206, are not propagated to the exterior of the compressor, but a sectional area of the enclosed container 206 becomes large, thereby creating a problem in that a heat quantity at the high pressure chamber 206a side is apt to be transferred to the liquid refrigerant and/or the intake gas refrigerant to thereby further lower the compression efficiency.
Conversely, when the wall of the low pressure chamber 206b is smaller in thickness, the refrigerant noise or the resonant noise of the enclosed container 206 are propagated to the exterior of the compressor, thereby creating a problem in that especially the low noise characteristics of the scroll compressor are deteriorated.
It is required to ensure a distance between the end of the motor and the oil level at a lubricating oil sump provided at the bottom of the high pressure chamber 206a in order to prevent an outflow of lubricating oil to the exterior of the compressor and/or a power loss caused by agitating the lubricating oil in the sump when a rotor of a motor disposed above the sump rotates at high speed. As the result, the high pressure chamber 206a is larger in height, thereby creating a problem in that the compressor is large-sized. Moreover, since the lubricating oil sump is at the bottom apart from the compression unit, during the stopping the compressor for a long time, the lubricating oil at a bearing slidable portion flows into the sump, thereby creating a problem in that, when the compressor restarts, the bearing slidable portion may seize.
In the construction that the fixed scroll 202 contacts at one side with the low pressure chamber 206b and at the other side with the compression chamber, as disclosed in FIG. 2b of Japanese Laid-Open Patent Publication No. 55-46046, pressure in the compression chamber swells the central portion of fixed scroll 202 toward the low pressure chamber 206b. As the result, an axial gap at the compression chamber is enlarged to increase a leakage amount of compressed gas refrigerant, thereby creating a problem in that the compression efficiency remarkably lowers.
To solve the above-mentioned problems, as disclosed in FIG. 4 of Japanese Laid-Open Patent Publication No. 55-46046, a construction has been proposed in which a back pressure chamber is formed at the rear of the fixed scroll, fluid pressure of the back pressure chamber is applied to the fixed scroll, so that the compression chamber pressure restrains the swollen central portion of the fixed scroll, thereby preventing lowering of compression efficiency while keeping a proper axial gap at the compression chamber.
However, it is required for the above-mentioned construction of Japanese Laid-Open Patent Publication No. 55-46046 to provide a particular back pressure chamber at the rear side of fixed scroll, thereby creating a problem in that the member of parts increases to raise the manufacturing cost, the space for installing the low pressure chamber is reduced, and the gas-liquid separation efficiency of the intake refrigerant deteriorates. Hence, a scroll gas compressor has been desired which is small-sized, high in compression efficiency, superior in low vibrations, low noise characteristics, durability, and processes a wide range of operating speeds.